| 题名 | 低温Yb:YAG再生放大器技术研究 |
| 作者 | 李响 |
| 学位类别 | 硕士 |
| 答辩日期 | 2011 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 李学春 |
| 关键词 | Yb:YAG 低温 再生放大器 LD |
| 其他题名 | Cooling Yb:YAG Regenerative Amplifier Technology |
| 中文摘要 | 近年来，随着InGaAs激光二极管的性能发展以及成本降低，利用其作为泵浦源的固体激光器 (Diode Pump Solid State Laser, DPSSL)因具有效率高、光束质量好、结构紧凑、寿命长、可获得高能量、大功率的稳定输出，而成为固体激光器发展的主要方向之一。 本论文的主要工作是针对大型高功率激光器重复频率低的问题，选用Yb:YAG晶体作为工作物质，对再生放大器进行了设计和实验研究。并利用Yb:YAG晶体在低温环境下优异的光学特性，实现了重复频率10Hz弱脉冲信号光的能量放大。本论文主要分为四个部分： 第一部分对整篇论文的研究背景、研究目的以及论文的结构作了简要的概述，明确了论文的研究意义。 第二部分是对再生放大器设计上进行阐述： （1）介绍了光学谐振腔设计理论，对其稳定性以及增益介质在其内部产生的热透镜效应进行了分析，并通过动态稳定理论研究了避免热扰动的工作方式。 （2）研究了高斯光束进入系统当中的模式耦合。 （3）通过能级方程，对脉冲信号在增益介质内部放大过程进行了研究，分析了再生放大器内部能量变化过程以及增益饱和效应。 （4）介绍了利用二元面板进行空间光束整形理论。 第三部分是整个低温再生放大器的设计工作，包括： （1）纳秒级信号脉冲源，它为后面的再生放大装置提供高稳定、高光束质量、光强空间分布光滑、脉冲形状在一定范围内可调的优质种子脉冲。 （2）再生放大器中谐振腔的选择与设计。 （3）使用激光二极管模块对Yb:YAG晶体进行端面泵浦，设计了一套用于激光二极管输出尾纤的透镜耦合系统，此系统可以很好的补偿像差，使泵浦光均匀的聚焦在增益介质上。 （4）设计了一套用于为Yb:YAG晶体进行降温处理的真空低温冷却系统，利用液氮作为冷媒，对Yb:YAG晶体进行间接式的冷却。并通过温度传感器实时测试温度情况，通过电磁开关对液氮的流入进行控制，能够使晶体温度控制在-170℃—-50℃，控制精度±1℃。 （5）介绍了再生放大器输出光束的整形系统。 第四部分对实验中的结果进行归纳、分析： （1）对晶体在不同温度下的荧光光谱进行了测量，讨论了光谱随温度而发生的变化。并计算了不同温度下再生放大器的小信号增益系数，分析了在温度低于-90℃的情况下，强烈ASE背底噪声信号的产生原因。 （2）初步实现了低温Yb:YAG再生放大器样机。信号光通过再生放大器可以得到10mJ的能量输出，总增益大于<10>上标<7>倍，稳定度±3%，方波扭曲度1.5。 （3）利用二元面板以及空间滤波器对高斯分布的输出光进行了空间整形处理，得到了4.5mm*4.5mm的平顶光束。 |
| 英文摘要 | In recent years, with the development of InGaAs laser diode performance and the cost reduction, solid-state lasers pumped by laser diode(Diode Pump Solid State Laser, DPSSL) with high efficiency, good beam quality, compact structure and long life, ability to get stable high energy or power output, becomes one of the main directions of solide-state laser. The main work of this thesis is the design and experimentally research of the regenerative amplifier with the use of Yb:YAG crystal as working substance to solve the low rate problem in high-power lasers. And we use the fine optical characteristics of Yb:YAG crystal at low temperature to achieve the weak laser pulse amplification at the rate 10Hz. The thesis is divided into four parts: The first part of the whole thesis gives a brief overview of the research background, purpose and the paper structure, and clears the research significance. The second part elaborates on the design of the regenerative amplifier: （1）Describe the design theory of optical resonator， analysis its stability and the thermal lens effect of the gain medium, and research the work to avoid thermal disturbances through the dynamicstability theory . （2）Research the mode coupling into the system of the Gaussian beam. （3）Through the Energy level equation, the signal amplification process of the laser pulse in the gain medium has been studied, and the energy changing process in the regenerative amplifier and the gain saturation effect are analyzed. （4）Introducing the theory of spatial beam shaping with the use of dual beam. The third part is the design of the low-temperature regenerative amplifier, including: （1）Nanosecond signal pulse source, it provides fine seed pulses with high stability , high beam quality, smooth distribution of light intensity, which shape can be adjusted within a certain range. （2）Designed a vacuum cryogenic cooling system for the Yb:YAG crystal, using liquid nitrogen as a refrigerant indirectcooling to Yb:YAG crystal. Temperature sensors test the real temperature condition and the magnetic switch control the inflow of nitrogen, these can make the Yb:YAG crystal temperature at -170℃—-50℃, and the precision at ±1℃. （3）Yb:YAG is end-pumped by laser diode module, and a lens coupling system is designed for the laser diode, which can compensate astigmation and make the pump laser to focus on the gian medium equably. （4）The selection and design of regenerative amplifier cavity. The fourth part summarized and analysed results of the experiment, analysis: （1）The fluorescence spectras at different temperatures are measured, and the change of the spectral is discussed. The signal gain coefficients in the regenerative amplifier at different temperatures are calculated, and the reason of the ASE at the temperature below -90 ℃ is analysed. （2）The low temperature Yb:YAG regenerative amplifier is built initially. Signal laser raises to 10mJ through the amplifier, the total gain over <10>上标<7>, stability factor ±3%, and square-pulse distortion 1.5. （3）Use the Dual Panel and spatial filter to shape the output laser with the Gaussian distribution, then 4.5mm*4.5mm flat-topped beam is achieved. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16694]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 李响. 低温Yb:YAG再生放大器技术研究[D]. 中国科学院上海光学精密机械研究所. 2011. |
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